(a) Technical Field
Embodiments of the present disclosure are directed to an optical modulation device, a driving method thereof, and an optical display device using the same, and more particularly, to an optical modulation device including liquid crystals, a driving method thereof, and an optical display device using the same.
(b) Discussion of the Related Art
Optical display devices that use an optical modulation device for modulating characteristics of light have been recently developed.
For example, for a 3-dimensional (3D) optical display device, an optical modulation device is used to divide an image into different viewpoints to be transmitted to a viewer so that the viewer can perceive the image as a stereoscopic image.
An optical modulation device that can be used in an autostereoscopic 3D image display device includes a lens, a prism, etc., that can alter a path of light to transmit the image of the display device to a desired viewpoint.
As such, a direction of incident light can be altered using light diffraction through phase modulation thereof.
When polarized light passes through an optical modulation device such as a phase retarder, its polarization state is changed.
For example, when circularly polarized light is incident on a half-wave plate, the circularly polarized light is output with its rotation direction reversed.
For example, when left circularly polarized light passes through the half-wave plate, right circularly polarized light is output.
In this case, a phase of the circularly polarized light shifts according to an optical axis of the half-wave plate, that is, a slow axis.
Specifically, when the optical axis of the half-wave plate rotates in-plane by φ, a phase of the outputted light shifts by 2φ.
Thus, when the optical axis of the half-wave plate is spatially rotated in an x-axis direction by 180° (π radians), the outputted light may be phase modulated or shifted by 360° (2π radians) in the x-axis direction.
As such, when an optical modulation device induces a phase shift from 0 to 2π depending on position, a diffraction grating or prism for altering or diffracting the transmitted light can be implemented.
Liquid crystals may be used to adjust the optical axis of an optical modulation device, such as a half-wave plate, according to the position thereof.
In an optical modulation device implemented as a phase retarder using liquid crystals, the long axes of liquid crystal molecules, which are arranged by applying an electric field to a liquid crystal layer, may be rotated to change the phase modulation according to position.
The phase of the light output after passing through an optical modulation device may be determined by the directions of the longer axes of the aligned liquid crystal molecules, that is, an azimuthal angle.
A lens may be implemented using an optical modulation device that uses liquid crystal molecules to generate continuous phase modulation by aligning the liquid crystal molecules in a desired direction by application of a lens voltage.
However, in a region where there are strong horizontal and vertical fields due to large voltage differences, texture may be generated in 3D mode since alignment of the liquid crystal molecules is unstable.